Device for supporting a seated person and method for adjusting, designing and/or manufacturing such a device

ABSTRACT

The invention relates to a device for supporting a seated person, comprising a seat and a support for the lumbar-thoracic transition region, which is connected to the seat, and characterized by an adjustable lumbar-sacral support, which is mounted at the location of the lower side of the support for the lumbar-thoracic transition region. Preferably, an adjustable support is furthermore provided for the thoracic-cervical transition region, which support is mounted at the location of the upper side of the support for the lumbar-thoracic transition region.

[0001] The invention relates to a device for supporting a seated person,comprising a seat and a support for the lumbar-thoracic transitionregion, which is connected to the seat.

[0002] Such backrests are well-known, and they are usually connected tothe rear side of the seat by means of a fixed pivot. Frequently, theyconsist of a basic frame, with respect to which part of the support canbe moved to the front in the lumbar region so as to follow theindividual curvature of the spinal column in the lumbar region(indicated by letters “AB” in FIG. 1). Moving said support part to thefront can be done mechanically or pneumatically. Frequently, saidsupporting region can be adjusted in vertical direction as well, sincethe location of the deepest point of the lumbar region of the spine canvary with each individual person. One drawback of these solutions isthat only a marginal individual optimization can be achieved. Theadjusting range for moving the lumbar support to the front with respectto the seat is limited.

[0003] U.S. Pat. No. 3,121,592 relates to a chair intended to providemore comfortable support for the lumbar region of the occupant's back.To this end, the chair according to this publication comprises a fixedshoulder engaging panel and an automatically self-adjusting lumbarengaging member.

[0004] French patent application 1.303.089, concerns a similar chair,wherein the adjustable support is positioned lower, i.e. more towardsthe seat.

[0005] Shortcomings of the prior art will be explained by means of FIG.2 attached to this description, which shows several possible forms ofthe lumbar region of the spine, ranging from a concave back or lordosis(numerals 1 and 2), via a flat back (3) to a convex back or kyfosis (4),whilst the posture of the upper body remains unchanged. The position onthe seat relative to the backrest shifts forward accordingly. FIG. 3shows the same postures for the concave back and the flat back, whilstthe position of the seat remains unchanged. The difference isremarkable. It is impossible to bridge this difference with existingspecific lumbar supports. Moreover, the posture is influenced to asignificant degree by moving the lumbar support to the front, whilst thedesired posture has already been determined earlier by adjusting theangle of the backrest. From a functional point of view, this is notlogical. Furthermore, the extent of support in transverse directiondecreases when the lumbar support is moved to the front. As a result,the desired lateral support of the pelvis decreases. This also is notlogical from a functional point of view.

[0006] The basic frame of existing backrests usually consists of a hardshell which is lined with a foam, or of a frame in which foam-coverednon-sag springs or webs are stretched in transverse direction. Suchconstructions exhibit a limited capability of adapting to the individualshape of the back and the pelvis. Usually the thoracic-cervicaltransition region (indicated by the letter “C” in FIG. 1) is notsupported, and in those cases where it is attempted to do so by formingthe upper part of the backrest with a curvature to the front, saidcurvature is not individually adjustable.

[0007] Some important drawbacks of existing forms of individuallyadjustable posture support are that, from a functional viewpoint, theadjusting process is not based on a logical order, that the adjustingranges are too small, and that there is no adjustable support for theupper part of the back. As a result, an optimum result is usually notachieved.

[0008] The object of the present invention is to provide an improveddevice of the type referred to in the introduction.

[0009] This objective is accomplished in that the device comprises anadjustable lumbar-sacral support, which is mounted at the location ofthe lower side of the support for the lumbar-thoracic transition region.Preferably, the lumbar-sacral support can be adjusted over a range whichenables forming both a convex support and a concave support togetherwith the support for the lumbar-thoracic transition region.

[0010] It is further preferred that an adjustable support is providedfor the thoracic-cervical transition region, which support is mounted atthe location of the upper side of the support for the lumbar-thoracictransition region.

[0011] Thus, the support of the lumbar-thoracic transition region, i.e.the part of the back that extends approximately from the ninth thoracicvertebra from above (T9) to the second or third lumbar vertebra fromabove (L2/L3), can be used both functionally and constructionally fordefining the desired posture first and subsequently supporting the lowerpart and preferably also the upper part of the back individually fromthere, irrespective of the shape of the individual back in sagittal andin transversal section. The individual posture support that can beachieved by this approach is maximal.

[0012] A special embodiment of this concept concerns a foldablesolution. This makes it possible to use this new concept of posturesupport also in wheelchairs which can be adjusted for width.

[0013] The invention functionally and constructionally plays along withthe essence of the sitting posture. The essence is that the position ofthe upper body in space is determined by the lumbar-thoracic transitionregion (FIG. 1:1), irrespective of the shape of the back (FIG. 2). Theshape of the back in the lumbar region defines the location of thelumbar-thoracic support with respect to the seat, starting from a fixedposture of the ischia in the seat. See FIGS. 2 and 3. In the case of aconcave back (lordosis; FIGS. 2:1 and 2), the intersecting point of thetangent line of the back support with the seat (FIG. 3) will be locatedin front (tangent T1) of the rear side of the seat, in the case of aconvex back (kyfosis) it will be located approximately at the rear side(tangent T2) of the seat. In order to achieve a satisfactory individualsupport, the backrest and the seat can be adjusted in forward-rearwarddirection with respect to each other, therefore. See also FIGS. 2 and 3.The adjusting range that can thus be achieved is much larger than ispossible with a specific lumbar support.

[0014] A stable, relaxed posture is characterized by a posture of thelumbar-thoracic transition region, which is about 25-35° off plumb (seatangle and sitting angle together about 115-125°, see FIG. 1: 3 and 4).Not only is the torso given its stability in this posture, but also thehigher thoracic-cervical transition region is maximally relaxed. In thisposture the head is in a well-balanced posture on the torso, with aminimum amount of effort being required. As a result of the definitionthat is used, this posture is independent of the shape of a person'sback and, within certain margins, it is the same for all persons (FIG.2). Furthermore, the ratio between the seat angle and the sitting angleneeds to be optimized in order to create maximum seating comfort. Acorrect ratio between the two angles (FIG. 1: 3 and 4) eliminates thefrictional forces on the seat. In order to achieve an individualoptimization of this stable, relaxed posture the spinal column ispreferably supported in its natural individual curvature as much aspossible. Only in this manner is it possible to realise an optimallyadvantageous internal load while sitting. The intervertebral discs, theligaments and the capsules in the spinal column are loaded in the mostadvantageous manner possible, while sufficient space for the bellyremains. The neurophysiologic control of the posture and thesensorimotor feedback are optimal.

[0015] Not only does the present invention maximally accommodate theindividual lumbar and thoracic shape of the spinal column, it alsoprovides a logical and unequivocal adjusting procedure for achievingthat result. To a certain extent this also guarantees that an optimumsupport is actually achieved in practice.

[0016] Since the posture in space of the lumbar-thoracic transitionregion (FIG. 1:1) constitutes the essence of the sitting posture, it isa characterizing feature of the new posture support concept that thecentral support of the lumbar-thoracic transition region of the spinalcolumn forms the basis, both functionally and constructionally, of theposture support in longitudinal section and in cross-section.

[0017] The principle of the basic support is shown in side elevation inFIG. 4. The supporting element 41 is pivotably mounted on a frame 42 andcan be adjusted individually for height H, by means of a telescopic arm43, and for depth D with respect to the seat 44. To this end, the seat44 is attached to the frame 41 by means of linear guides 45. FIG. 5shows a front view and a side view of the basic supporting element 41.FIG. 6 is a top plan view. A relatively small rectangular supportingelement 46 centrally supports the lumbar-thoracic region of the spine,upwards from the deepest point of the lumbar region. The posture of theupper body 47 in space is thus defined. In the lumbar region aconstruction is fitted in transverse direction, to both outer sides ofwhich construction a narrow, preferably flexible band 48 is attached,which band 48 extends in upward direction from the deepest point of thelumbar region. Said band 48 easily adapts to the individual shape of theback and provides basic support in transverse direction. By means ofthis central supporting element 41 a desired posture can be individuallydefined. If a general, stable, relaxed posture is desired, saidsupporting element 41 can be offered or be pre-set in a more or lessfixed angle in a range of 25° to 35° e.g. about 30° off plumb. Afterall, said angle is independent of the individual back type.

[0018] In this respect, reference may be had to FIG. 2. The position inforward-rearward direction with respect to the seat, as well as theindividual height with respect to the deepest point of the lumbarregion, still need to be adjusted individually, of course. Care shouldbe taken that a proper ratio between the seat angle and the sittingangle be maintained (FIG. 1: 4 and 3). In principle it is possible todefine the individual posture, the position of the upper body in space,by means of this basic supporting element. What comes after that isindividual support.

[0019]FIG. 7 shows a functional side view. The supporting element 71 ofthe pelvis is pivoted to the bottom side of the central supportingelement 41. The pivot pin 72 extends in transverse direction near thedeepest point of the lumbar region of the spine. FIG. 8 shows a frontview and a side view of a construction principle. The bands that areshown in the drawing of FIG. 8 jointly form the specific lumbar support.Since said element can move to the front and to the rear with respect tothe supporting element 41, lumbar lordosis (FIG. 2:1) as well as lumbarkyfosis (FIG. 2:4), and all possibilities therebetween, can beaccommodated . This element 71 also preferably comprises a flexible,non-stretch material 73 that follows the individual contour of the bodyin transverse direction.

[0020] At the upper side of the central supporting element 41 thethoracic region of the spine (FIG. 1: BC) is further supported in upwarddirection by a flexible supporting element 91, which is attached to arelatively narrow, horizontal constructional element 92 in such a manneras to be centrally adjustable, which latter element 92 can beindividually positioned behind the thoracic-cervical transition regionand which is attached at its bottom side to both sides of the centralsupporting element 41, possibly continuing to the pelvis supportingelement 71. FIG. 9 shows the functional principle thereof. The manner ofattachment and the triangular shape of the flexible material 91 assistin providing a maximum adaptation to the individual thoracic body shapewhen the supporting element 41 is loaded. FIG. 10 shows a front view ofa functional principle.

[0021] In principle all flexible supporting elements can be designed soas to enable individual tensioning. The backrest can be lined with athin layer of foam upholstered with a stretch-type cover.

[0022] The individual optimization of a semi-active, stable and relaxedsitting posture starts with the pre-setting of the central supportingelement, which is about 25-30° off plumb. Starting from this posture,possible fine-adjustments can be made. The other supporting elements areloosened, so that they do not have a supporting function. Then thecentral supporting element is adjusted with respect to the seat inaccordance with the user's back type. In the case of lordosis, it isadjusted before the rear side of the seat. The angle that the seatbuilds with the horizontal is set so that the angle between the loadedseat (i.e. a seat in which a person is seated) and the loaded backrestis about 95-115°, preferably about 95-105°. These ranges are generallypreferred for the angle between the seat and the backrest. Frictionalforces are thus eliminated. After the user has sat down on the seat inaccordance with the seat instructions (some seats distribute thepressure best when the ischia are positioned at the intended spot on theseat), fine-adjustment takes place. The posture of the centralsupporting element with respect to the seat and the height with respectto the back are verified and possibly adjusted. Possibly, the angle ofthe central supporting element is adjusted in order to optimise theposture. The criterion for this is that the head must take up a relaxedposture on the torso. Then the pelvis supporting element is movedtowards the pelvis and fixed in posture. Following that, the central,horizontal constructional element is positioned near thethoracic-cervical transition region approximately 15 mm outside thebody. The flexible supporting material is tensioned over saidconstructional element in downward direction. This approach provides anoptimum individual posture support.

[0023] In principle the present invention can be used in all types ofchairs that are intended to enable individual optimization of theposture support. Especially car or aircraft seats, armchairs, officechairs and wheelchairs can be considered in this connection. The conceptis eminently suited for use in foldable wheelchairs , because of theflexibility of the supporting material. Furthermore, it is conceivableto use pre-formed supporting elements of a non-flexible material forsome applications. In principle the adjustments can be so designed thatthey can be operated and fixed by the user himself. This principle, orpart thereof, is also suitable for posture support in recliningbicycles. The individually adjustable constructional element in thethoracic-cervical transition region (FIG. 1:C) defines the posture sotypical of reclining bike-riders by a considerable thoracic kyphosis.The use of perforated material not only provides a perfect individualsupport, but it also makes it possible to meet other importantrequirements, such as moisture regulation.

What is claimed is:
 1. A device for supporting a seated person,comprising a seat and a support for the lumbar-thoracic transitionregion, which is connected to the seat, an adjustable lumbar-sacralsupport, which is mounted at the location of the lower side of thesupport for the lumbar-thoracic transition region, characterized in thatthe support for the lumbar-thoracic transition region and seat can beadjusted for height with respect to each other.
 2. A device according toclaim 1, wherein the lumbar-sacral support can be adjusted over a rangewhich enables forming both a convex support and a concave supporttogether with the support for the lumbar-thoracic transition region. 3.A device according to claim 1, wherein an adjustable support isfurthermore provided for the thoracic-cervical transition region, whichsupport is mounted at the location of the upper side of the support forthe lumbar-thoracic transition region.
 4. A device according to claim 1,wherein the lumbar-sacral support and/or the support for thethoracic-cervical transition region is/are pivoted to the support forthe lumbar-thoracic transition region, being capable of pivotingmovement about a substantially horizontal, imaginary axis.
 6. A deviceaccording to claim 1, wherein the support for the lumbar-thoracictransition region and the seat can be adjusted to the front and to therear with respect to each other.
 7. A device according to claim 1,wherein the angle of the support for the lumbar-thoracic transitionregion is adjustable with respect to the seat and/or wherein the seat isadjustable relative to the horizontal.
 8. A device according to claim 1,wherein at least one of said supports is made of a flexible, low-stretchmaterial that easily adapts to the body contour.
 9. A device accordingto claim 1, wherein at least one of said supports comprises a shellhaving an anatomic shape, which is lined with a foam-like material. 10.A method for adjusting, designing and/or manufacturing a device forsupporting a seated person, comprising a seat, a support for the lumbarthoracic transition region, and a lumbar-sacral support, wherein saidperson sits down on the seat and leans against the support for thelumbar-thoracic transition region, after which the position of thelumbar-sacral support is adapted to the posture of the lumbar region ofsaid person and wherein the support for the lumbar-thoracic transitionregion is adjusted prior to adapting the position of the lumbar-sacralsupport.
 12. A method according to claim 10, wherein the lumbar-sacralsupport is adjusted to form a convex support together with the supportfor the lumbar-thoracic transition region.
 13. A method according toclaim 10, wherein said device furthermore comprises a support for thethoracic-cervical transition region, and wherein, once said person leansagainst said support for the lumbar-thoracic transition region, andpreferably after the posture of the lumbar-sacral support has beenadapted, the position of said support is adapted to the individualcurvature of the thoracic-cervical transition region of said person. 14.Wheelchair or chair comprising a device according to claim
 1. 15. Adevice according to claim 1, wherein the angle that the seat builds withthe horizontal is set so that the angle between the loaded seat and theloaded backrest is in the. range from about 95° to about 115°.
 16. Adevice according to claim 2, wherein an adjustable support isfurthermore provided for the thoracic-cervical transition region, whichsupport is mounted at the location of the upper side of the support forthe lumbar-thoracic transition region.
 17. A device according to claim2, wherein the lumbar-sacral support and/or the support for thethoracic-cervical transition region is/are pivoted to the support forthe lumbar-thoracic transition region, being capable of pivotingmovement about a substantially horizontal, imaginary axis.
 18. A deviceaccording to claim 2, wherein the angle that the seat builds with thehorizontal is set so that the angle between the loaded seat and theloaded backrest is in the range from about 95° to about 115°.
 19. Adevice according to claim 2, wherein the support for the lumbar-thoracictransition region and the seat can be adjusted to the front and to therear with respect to each other.
 20. A device according to claim 2,wherein the angle of the support for the lumbar-thoracic transitionregion is adjustable with respect to the seat and/or wherein the seat isadjustable relative to the horizontal.
 21. A device according to claim2, wherein at least one of said supports is made of a flexible,low-stretch material that easily adapts to the body contour.
 22. Amethod according to claim 12, wherein said device furthermore comprisesa support for the thoracic-cervical transition region, and wherein, oncesaid person leans against said support for the lumbar-thoracictransition region, and preferably after the posture of the lumbar-sacralsupport has been adapted, the position of said support is adapted to theindividual curvature of the thoracic-cervical transition region of saidperson.